Winston S. Churchill. The Second World War, vol. 3In Churchill's history of The Second World War he wrote of his emotions upon hearing that Japan had attacked United States forces at Pearl Harbor on December 7, 1941. Only "silly people, and there were many," underestimated American strength. For him, the entry of the United States into the war meant that the ultimate outcome—favorable for his country—was now assured. Feeling "the greatest joy" that the attack had arrayed his mother's country on the side of Britain, he "went to bed and slept the sleep of the saved and thankful."